检查哈希函数中的现有文件是否产生错误的结果

Question

下面的代码扫描目录中的新文件，并为找到的每个文件计算哈希值-将其存储在Documents目录的子文件夹“ _HASH”中。我遇到的问题是，当尝试实现一个功能来检查文件是否已经计算出其哈希值（在“ _HASH”文件夹中）时，它似乎无法正常工作。

#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <string.h>
#include <errno.h>
#include <sys/inotify.h>
#include <openssl/sha.h>

int main (int argc, char *argv[])
{
        int fd;
        int wd;
        unsigned char c[SHA512_DIGEST_LENGTH];
        int i;
        SHA512_CTX mdContext;
        int bytes;
        unsigned char data[1024];
        const int event_size = sizeof(struct inotify_event);
        const int buf_len = 1024 * (event_size + FILENAME_MAX);
        char *directory = "/home/joe/Documents/";
        char *hashDirectory = "/home/joe/Documents/_Hash/";
        char hashInBuf[500];
        char hashOutBuf[500];
        fd = inotify_init();

        if (fd < 0) {
          perror("inotify_init");
        }

        wd = inotify_add_watch(fd, "/home/joe/Documents", IN_CREATE);
        while (1) {
          char buff[buf_len];
          int no_of_events, count = 0;
          //SEARCH FOR NEW FILES WITHIN DIRECTORY
          no_of_events = read (fd, buff, buf_len);
          while (count < no_of_events) {
            struct inotify_event *event = (struct inotify_event *)&buff[count];
            if (event->len) {
              if ((event->mask & IN_CREATE))
              if(!(event->mask & IN_ISDIR)) {
                printf("The file %s has been created\n", event->name);
                printf("%s\n", directory);

                //Conjoin directory and filename
                snprintf(hashInBuf, sizeof(hashInBuf), "%s/%s", directory, event->name);
                snprintf(hashOutBuf, sizeof(hashOutBuf), "%s/%s.txt", hashDirectory, event->name);
                FILE *ftest=fopen(hashInBuf, "rb");
                FILE *ftest2=fopen(hashOutBuf, "wt");
                //HASH FUNCTION
                SHA512_Init (&mdContext);
                while ((bytes = fread (data, 1, 1024, ftest)) != 0)
                    SHA512_Update (&mdContext, data, bytes);
                SHA512_Final (c,&mdContext);
                for(i = 0; i < SHA512_DIGEST_LENGTH; i++){
                  fprintf(ftest2, "%02x", c[i]);
                  printf("%02x", c[i]);
                }

                fclose (ftest);
                fclose (ftest2);
                fflush (stdout);
              }
            }
            count += event_size + event->len;
          }
        }
        return 0;
}

下面的代码是我想要在上面的代码中实现的代码，但是我不确定将代码放置在何处。到目前为止，尝试执行的结果（在代码中的各个点）似乎总是确定文件存在。

if(access(hashOutBuf, F_OK) != -1) {
              printf("File exists\n");
              //COMPARE HASH AGAINST EXISTING FILE
            }